Cleaning Solution and Cleaning Method of a Semiconductor Device

ABSTRACT

A cleaning method for removing foreign bodies during the fabrication of semiconductor devices including treating a substrate with a cleaning solution including an oxidizer to form a chemical oxide layer and then removing the chemical oxide layer, thereby removing foreign bodies from a surface of the semiconductor substrate. Accordingly, the foreign bodies can be substantially removed from the surface of the substrate without corroding a metal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.11/502,011, filed Aug. 10, 2006 which is a divisional of U.S. patentapplication Ser. No. 10/859,815, filed on Jun. 3, 2004, now U.S. Pat.No. 7,105,475, the disclosures of which are each hereby incorporated byreference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates, generally, to cleaning solutions andcleaning methods of semiconductor devices, more particularly, tocleaning solutions capable of removing foreign bodies without corrodingmetals used in fabricating semiconductor devices, and cleaning methodsusing the cleaning solutions.

BACKGROUND OF THE INVENTION

Generally, a semiconductor manufacturing process comprises unitprocesses such as a thin film process for forming a dielectric layer anda conductive layer on a semiconductor substrate, a photolithographicprocess for patterning the dielectric layer and conductive layer to adesired pattern, a contact window process for connective conductivematerial layers (or patterns) to each other, a chemical mechanicalpolishing (CMP) process for planarizing surfaces of the material layers,etc.

During the manufacturing processes, undesirable foreign bodies, e.g.,small particles, metal impurities and organic contaminants, etc, mayremain on the surfaces of material layers, thereby causing problems insubsequent processes or in a manufactured device. For instance, theforeign bodies remaining on an interface between conductive materiallayers may deteriorate contact resistance characteristics of themanufactured device. In addition, if an upper material layer is formedon a lower material layer with foreign bodies on a surface thereof, theupper material layer may exhibit bad step coverage, an irregularsurface, or poor growth. Therefore, a cleaning process is performed toremove foreign bodies on a material layer between the unit processes.

SCl is a conventional cleaning solution used in semiconductormanufacturing and includes a mixture of hydrogen peroxide (H₂O₂),ammonium hydroxide (NH₄OH) and deionized water. Although SCl does notcause particular problems to polysilicon, silicon nitride, and oxide,SCl contains hydrogen peroxide that causes problems to metals used infabricating semiconductor devices because hydrogen peroxide is a strongoxidizer. For instance, the hydrogen peroxide corrodes various metalsused in processes for fabricating semiconductor devices and has adisadvantage of requiring a high temperature for cleaning.

Therefore, a need exists for cleaning solutions that are capable ofremoving foreign bodies without corroding metals used in semiconductorfabrication, and cleaning methods using the cleaning solutions.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide cleaningsolutions that are capable of removing foreign bodies without corrodinga metal, and cleaning methods using the cleaning solutions.

According to an exemplary embodiment of the present invention, acleaning solution includes an oxidizer, deionized water, a fluorinebased deoxidizer and a surface charge controlling agent.

According to another exemplary embodiment, an oxidizer of a cleaningsolution serves to form a chemical oxide layer on a surface of a targetlayer to be cleaned. A fluorine based deoxidizer of the cleaningsolution serves to remove the chemical oxide layer formed by theoxidizer. Therefore, when a substrate with a material layer havingforeign bodies is treated with the cleaning solution, the surface of thematerial layer is oxidized by the oxidizer to form the chemical oxidelayer. Simultaneously, the chemical oxide layer formed by the oxidizeris removed by the fluorine based deoxidizer. In this case, by oxidizingthe surface of the material layer, the foreign bodies that were on thesurface of the material layer are now located on the chemical oxidelayer. Accordingly, the foreign bodies are removed while the chemicaloxide layer is removed.

According to another exemplary embodiment, a surface charge controllingagent of the cleaning solution changes a surface potential (i.e., a zetapotential) of particles, or foreign bodies, removed from the surface ofthe material layer. For example, the surface charge controlling agentchanges the zeta potentials of the material layer and the foreign bodiesremoved from the material layer to be either a strong negative or astrong positive zeta potential, thereby generating an electricalrepulsive force between the removed foreign bodies and the materiallayer. Therefore, the surface charge controlling agent prevents theforeign bodies removed from the surface of the material layer from beingre-adsorbed on the surface of the material layer such that the foreignbodies are completely removed from the material layer.

According to another exemplary embodiment, the fluorine based deoxidizerhas a high etch selectivity with respect to oxide layers, e.g., a metaloxide and a silicon oxide.

According to another exemplary embodiment, the oxidizer in the cleaningsolution does not corrode metals. Accordingly, the foreign bodies can beremoved without erosion of a metal.

According to another exemplary embodiment of the present invention, acleaning solution includes about 0.01 wt % of a surface chargecontrolling agent, about 10 wt % of a fluorine based deoxidizer andabout 5 wt % of an oxidizer.

According to another exemplary embodiment, the fluorine based deoxidizerincludes hydrofluoric acid, hydroboron tetrafluoric acid, ammoniumfluoride or any combination thereof.

According to another exemplary embodiment of the present invention, theoxidizer includes an iodine based oxidizer, nitric acid, phosphoric acidor any combination thereof. Further, the iodine based oxidizer includesammonium iodine oxide, potassium iodine oxide, lithium iodine oxide,calcium iodine oxide, barium iodine oxide, potassium iodine, ammoniumiodine or any combination thereof.

According to another exemplary embodiment, the surface chargecontrolling agent includes an organic acid, a surfactant or anycombination thereof. The organic acid includes citric acid, atricarboxylic acid, tartaric acid, succinic acid, malic acid, asparticacid, glutaric acid, adipic acid, suberic acid, oxalic acid, aceticacid, fumaric acid or any combination thereof.

According to another exemplary embodiment, the surfactant includes anegative ion surfactant or a positive ion surfactant. The negative ionsurfactant or the positive ion surfactant is adsorbed on surfaces of theparticles and changes the zeta potential of the particles.

According to another exemplary embodiment, the above cleaning solutionsubstantially removes foreign bodies from a surface of the materiallayers formed in the processes for fabricating semiconductor devices,such as a metal layer, a metal nitride layer, a polysilicon layer or ametal silicide layer.

According to another exemplary embodiment, the cleaning solution of thepresent invention may be used in cleaning methods to remove not only theforeign bodies occurring in processes for fabricating semiconductordevices but to also remove foreign bodies on a surface of a metal.

According to still another exemplary embodiment of the presentinvention, a cleaning method comprises the step of treating a substratewith a cleaning solution including an oxidizer, deionized water, afluorine based deoxidizer, and a surface charge controlling agent.Further a surface of the substrate is oxidized by the oxidizer to form achemical oxide layer, and the chemical oxide layer is removed by thefluorine based deoxidizer at the same time. Accordingly, foreign bodiesare removed from the surface of the substrate. Strong electric repulsiveforces are generated between surfaces of the removed foreign bodies andthe substrate due to the surface charge controlling agent.

According to another exemplary embodiment the present invention, acleaning method comprises oxidizing a substrate to form an oxide layeron a surface thereof and then removing the oxide layer.

In another exemplary embodiment, the forming of the oxide layercomprises treating the substrate with a solution including an oxidizer.

In another exemplary embodiment, removing the oxide layer comprisestreating the substrate with a solution comprising a fluorine baseddeoxidizer, a surface charge controlling agent and deionized water.

According to still another exemplary embodiment of the presentinvention, a cleaning method comprises treating a substrate with a firstsolution comprising an oxidizer, rinsing the substrate with deionizedwater to remove the first solution comprising an oxidizer, drying thesubstrate, and treating the substrate with a second solution comprisinga surface charge controlling agent, a fluorine based deoxidizer and adeionized water.

According to another exemplary embodiment, after treating the substratewith the second solution, the substrate may be treated with the firstsolution comprising the oxidizer, rinsed with deionized water to removethe first solution and then dried.

These and other exemplary embodiments, features, aspects, and advantagesof the present invention will be described and become apparent from thefollowing detailed description of the exemplary embodiments when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 3 illustrate a cleaning method, according to anexemplary embodiment of the present invention.

FIGS. 4 through 8 illustrate a metal interconnection process using acleaning method, according to another exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. This invention may, however, be embodied indifferent forms and should not be constructed as limited to theexemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the thickness of layers and regionsare exaggerated for clarity. It will also be understood that when alayer is referred to as being “on” another layer or substrate, it can bedirectly on the other layer or substrate or intervening layers may alsobe present.

In the specification, a “substrate” should be understood as anysemiconductor substrate structure having a layer. For example, thesubstrate includes a substrate with an insulating layer (or aninsulating pattern) and a conductive layer (or a conductive pattern),and a resultant structure of semiconductor substrate formed by aconventional photolithographic process. In addition, the substrate mayrefer to a metallic surface with a specific shape.

The present invention relates to cleaning solutions and cleaning methodsused in processes for fabricating semiconductor devices. The cleaningsolutions and the cleaning methods may also be applied to cleaning ametallic surface.

FIGS. 1 to 3 illustrate a cleaning method in accordance with anexemplary embodiment of the present invention. FIG. 1 is across-sectional view showing foreign bodies 103, such as microparticles, metal foreign bodies and organic determinants, on a substrate101. The substrate 101 may include various metal layers formed inprocesses for fabricating semiconductors, for example, a metalinterconnection, a polysilicon layer, a metal nitride layer, a metalsilicide layer, etc.

Referring to FIG. 2, a surface of the substrate 101 is oxidized to forma chemical oxide layer 105 with a specific thickness (t2). Therefore,the foreign bodies 103 remain on the surface of the chemical oxide layer105. The chemical oxide layer 105 is formed by an oxidizer. Preferably,the oxidizer is an iodine based oxidizer, nitric acid, phosphoric acidor any combination thereof. The iodine based oxidizer may includeammonium iodine oxide (NH₄IO₃), potassium iodine oxide (KIO₃), lithiumiodine oxide (LilO₃), calcium iodine oxide (CalO₃), barium iodine oxide(BalO₃), potassium iodine (KI), ammonium iodine (NH₄I) or anycombination thereof.

In a case where the substrate 101 is polysilicon, the iodine basedoxidizer forms a silicon oxide layer (SiO_(x)) on a surface of thepolysilicon substrate as a thin protection layer, for example, a silicondioxide (SiO₂) layer. In a case where the substrate 101 is tungsten, theiodine based oxidizer reacts with the tungsten substrate to form astable tungsten trioxide (WO₃) layer on the surface of the tungstensubstrate, wherein the stable tungsten trioxide (WO₃) layer acts as athin protection layer.

Referring to FIG. 3, the chemical oxide layer 105 is etched using afluorine based deoxidizer. The fluorine based deoxidizer may includehydrofluoric acid (HF), boron hydroboron tetrafuloric acid (HBF₄),ammonium fluoride (NH₄F) or any combination thereof. In addition, as thefluorine based deoxidizer etches the chemical oxide layer 105, theforeign bodies 103 remaining on the chemical oxide layer 105 are removedfrom a surface of the substrate 101′.

Surface polarities of the removed foreign bodies 103 and the substrate101′ are the same, for example, strong negative or strong positive.Therefore, a strong electrical repulsive force is generated between thesurfaces thereof. As a result, re-adsorption of the foreign bodies 103on the surface of the substrate 101′ is prevented. The repulsive forcebetween the surfaces of the substrate 101′ and the foreign bodies 103 iscreated by a surface charge controlling agent. The surface chargecontrolling agent may change a zeta potential of a particle surface.Preferably, the surface charge controlling agent is an organic acid, asurfactant or any combination thereof. The organic acid dissociates inan aqueous solution and adsorbs on the surface of the particles (asubstrate or a surface of the foreign contaminant) to change the zetapotential of the surface to a strong negative zeta potential. Thesurfactant comprises a surfactant with a polarity, e.g., a negative ionsurfactant or a positive ion surfactant. The surfactant changes the zetapotential of the particles by being adsorbed on the surface of theparticles. Preferably, the organic acid includes, for instance, citricacid, a tricarboxycide accid, targteric acid, succinic acid, malic acid,aspatic acid glutaric acid, adipic acid, suberic acid, oxalic acid,acetic acid, rumaric acid or any combination thereof.

According to an exemplary embodiment of the present invention, acleaning solution comprises an oxidant, deionized water, a surfactantincluding fluoride and a surface charge controlling agent. It will beevident to those skilled in the art that the weight passage (wt %) ofcomponents composing the cleaning solution can be properly adjustedwithin the scope of the invention. For example, an exemplary embodimentof the present invention may include about 0.01 wt % of a surface chargecontrolling agent, about 10 wt % of a reducer, and about 5 wt % of anoxidizer.

According to another exemplary embodiment, a semiconductor substrate 101is treated with a cleaning solution in accordance with exemplaryembodiments of the present invention in a cleaning apparatus. Thecleaning apparatus may be a spin type, a spray type, a rotating-spraytype or a dip type.

It should be noted that the substrate 101 may include a thin film,wherein the thin film may be a metallic layer or a polysilicon layer.Preferably, the metallic layer includes a metal nitride, a metalsilicide, or any of the metals used in semiconductor fabricatingprocesses, e.g., tungsten, titanium, nickel, cobalt, copper, aluminum,etc.

Preferably, the oxidizer included in the cleaning solution does notcorrode a metal. For example, the oxidizer includes an iodine basedoxidizer, nitric acid, phosphoric acid, or any combination thereof. Theiodine based oxidizer is ammonium iodine oxide (NH₄OH₃), potassiumiodine oxide (KIO₃), lithium iodine oxide (BaIO₃)potassium iondine (KI),ammonium iodine (NH₄I) or any combination thereof. The surface of thesubstrate 101, or thin film, is oxidized by the oxidizer to form achemical oxide layer 105. That is, a partial thickness t2 of thesubstrate 101, or thin film, is replaced by the chemical oxide layer105. Therefore, foreign bodies 103 remaining on the surface of thesubstrate 101 are now located on a surface of the chemical oxide layer105.

The fluorine based deoxidizer selectively removes the chemical oxidelayer 105. Preferably, the fluorine based deoxidizer is hydrofluoricacid (HF), boron hydroboron tetrafluoric acid (HBF₄), ammonium fluoride(NH₄F) or any combination thereof. The fluorine based deoxidizer etchesthe chemical oxide layer 105 such that the foreign bodies 103 remainingon the chemical oxide layer 105 are removed from the surface of thesubstrate 101′ while the chemical oxide layer 105 is etched.

The surface charge controlling agent prevents the removed foreign bodies103 from re-adsorbing on the substrate 101′. That is, the surface chargecontrolling agent changes the surface charges of the substrate 101′ andthe removed foreign bodies 103 to the same polarity (i.e., a strongnegative or strong positive polarity). Therefore, an electricalrepulsive force is generated between the substrate 101′ and the removedforeign bodies 103 that prevents the removed foreign bodies from beingre-adsorbed on the surface of the substrate 101′. Preferably, thesurface charge controlling agent is an organic acid, a surfactant or anycombination thereof. The organic acid dissociates in aqueous solution toadsorb on the surface of a solid, e.g., the surfaces of a substrate orthin film and foreign bodies, to change the zeta potential of the solidto a strong negative.

Preferably, the organic acid includes, for example, citric acid, atricarboxylic acid, tartaric acid, succinic acid, malic acid, asparticacid, glutaric acid, adipic acid, suberic acid, oxalic acid, aceticacid, fumaric acid or any combination thereof.

The cleaning methods according to the above exemplary embodiments removeforeign bodies from a surface of a substrate or material layer andprevent the foreign bodies from re-adsorbing on the surface of thesubstrate or material layer, especially, from a surface of polysilicon.

According to another exemplary embodiment of the present invention, afirst solution comprising an oxidizer and a fluorine based deoxidizerand a second solution comprising a surface charge controlling agent anddeionized water are prepared. Preferably, the first solution maycomprise about 5 wt % of the oxidizer, and the second solution maycoprise about 0.01 wt % of the surface charge controlling agent andabout 10 wt % of the fluorine based deoxidizer.

According to another embodiment, a semiconductor substrate 101 or a thinfilm, is treated with the first cleaning solution. As a result, achemical oxide layer 105 is formed on the surface of the substrate 101,or thin film, by an oxidizer in the first solution. The chemical oxidelayer 105 serves as an oxidation barrier layer. That is, chemicaloxidation is blocked when the chemical oxide layer is thick enough toblock the diffusion of oxygen. Preferably, the chemical oxide layer 105is tens of angstroms thick.

Preferably, the oxidizer in the first solution does not corrode metals.For example, the oxidizer is an iodine based oxidizer, nitric acid,phosphoric acid or any combination thereof.

The iodine based oxidizer includes ammonium iodine oxide (NH₄IO₃),potassium iodine oxide (KlO₃), lithium iodine oxide (LiLO₃), calciumiodine oxide (CalO₃), barium iodine oxide (BalO₃), potassium iodine(KL), ammonium iodine (NH₄I) or any combination thereof.

Next, the substrate with the chemical oxide layer 105 is treated withthe second solution. Therefore, while the fluorine based deoxidizer inthe second solution etches the chemical oxide layer 105, foreign bodies103 are removed from a surface of the substrate 101′, or thin film. Inaddition, the surface charge controlling agent of the second solutionadheres to the surfaces of the removed foreign particles 103 and thesubstrate 101′, thereby causing the surfaces of the substrate 101′ andthe removed foreign bodies 103 to have the same polarity, e.g., a strongnegative polarity. Thus, the foreign bodies 103 are prevented fromre-adsorbing on the surfaces of the substrate.

Preferably, the substrate is rinsed with the deionized water to removethe first solution from the substrate before treating the substrate 101′with the second solution.

Similarly, after the substrate ′101 is treated with the second solution,the substrate ′101 is rinsed with deionized water to remove the secondsolution. Then, the substrate 101′ is dried.

According to the above cleaning method, the foreign bodies can beremoved from a substrate or thin film, e.g., a polysilicon substrate ora polysilicon thin film. In addition, the cleaning methods above canremove foreign bodies from a substrate or a thin film, in which thesubstrate or thin film comprises a metal, without corroding the metal.

According to another exemplary embodiment, the cleaning methods of thepresent invention may be used to clean a single wafer. That is, thesubstrate is treated with the first solution to form a chemical oxidelayer, then rinsed with a deionized water to remove the first solutionfrom the substrate, and then dried. Next, the substrate is treated withthe second solution to remove the chemical oxide layer. The substrate isthen rinsed with deionized water to remove the second solution anddried.

According to another exemplary embodiment of the present invention, thesubstrate may be treated with the first solution after treating thesubstrate with the second solution. As a result, the first solution mayeffectively prevent the formation of a water spot during a spin-dryprocess by making the surface of the substrate hydrophilic.

The above cleaning methods may be adapted to every process in thefabrication of a semiconductor device that requires a cleaning step. Forinstance, the cleaning methods may be used in a cleaning processperformed after forming a tungsten or an aluminum interconnection, acleaning process after forming a polysilicon gate or a metal gateincluding polysilicon and metal, a cleaning process after forming acontact window for connecting the lower to upper connections, or acleaning process after a chemical mechanical process (CMP).

According to yet another exemplary embodiment of the present invention,FIGS. 4 through 8 illustrate a method for forming a metal interconnectusing a cleaning method in accordance with an exemplary embodiment ofthe present invention.

Referring to FIG. 4, a lower metal interconnection 402 is formed on asubstrate 400. The lower metal interconnection 402 may be electricallyconnected to an active region of the substrate 400. For instance, thelower metal interconnection 402 may be formed by depositing a metalmaterial and then patterning thereof. After the metal material ispatterned, a cleaning process, in accordance with the exemplaryembodiments of the present invention, is carried out to form a lowermetal interconnection 402 with a clean surface.

Further, a dielectric layer 404 is formed on the lower metalinterconnection 402 and the substrate 400. Preferably, the insulatinglayer 404 is a silicon oxide layer.

Referring to FIG. 5, the insulating layer 404 is patterned to form acontact window 406 exposing the lower metal interconnection 402 by aphotolithographic process.

Referring to FIG. 6, using an aqueous solution comprising an oxidizer (afirst solution), a metal oxide layer 408 is formed on the exposed lowermetal interconnection 402. In this case, oxidation may occur not only onthe exposed surface of the lower interconnection 402 but along a portionof the lower interconnection 402 not exposed and along a lower portionof sidewalls in the contact window 406 as well.

Referring to FIG. 7, a metal oxide layer 408 is removed using a secondsolution comprising a fluorine based deoxidizer, a surface chargecontrolling agent and deionized water. In a case where the dielectriclayer 404 is an oxide layer, the dielectric layer 404 and the metaloxide layer 408 may be simultaneously etched. Therefore, a diameter anda bottom area of the contact window 406′ increases, thereby improvingthe contact resistor characteristic between an upper metalinterconnection, to be formed in a subsequent process, and the lowermetal interconnection 402′.

Referring to FIG. 8, a metal material is deposited on the dielectriclayer 404 to fill the contact window 406′. The metal material is thenpatterned to form an upper metal interconnection 410.

The upper metal interconnection 410 is cleaned using a cleaning processin accordance with the exemplary embodiments of the present invention.

The cleaning solution of the present invention substantially removesforeign bodies from a metallic surface or a polysilicon surface withoutcorroding a metal.

In addition, the cleaning solution of the present invention effectivelycleans a metallic or polysilicon surface at room temperature.

While the present invention has been described in connection withspecific and exemplary embodiments thereof, it will be understood bythose of ordinary skill in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A method of removing foreign bodies from a surface of a thin filmformed on a substrate during a process for fabricating a semiconductordevice, comprising: forming an oxide layer by oxidizing the surface ofthe thin film; and removing the oxide layer.
 2. The method of claim 1,wherein forming the oxide layer comprises treating the substrate with anaqueous solution comprising an oxidizer.
 3. The method of claim 2,further comprising, after removing the oxide layer: treating thesubstrate with the aqueous solution comprising the oxidizer.
 4. Themethod of claim 1, wherein removing the oxide layer comprises treatingthe substrate with the oxide layer into a solution comprising a fluorinebased deoxidizer, a surface charge controlling agent and a deionizedwater.
 5. The method of claim 2, wherein the oxidizer is an iodine basedoxidizer, nitric acid, phosphoric acid, or any combination thereof. 6.The method of claim 5, wherein the iodine based oxidizer is ammoniumiodine oxide, potassium iodine oxide, lithium iodine oxide, calciumiodine oxide, barium iodine oxide, potassium iodine, ammonium iodine orany combination thereof.
 7. The method of claim 4, wherein the oxidizeris an iodine based oxidizer, nitric acid, phosphoric acid or anycombination thereof, wherein the fluorine based deoxidizer ishydrofluoric acid, hydroboron tetrafluoric acid, ammonium fluoride orany combination thereof, and wherein the surface charge controllingagent is an organic acid, a surfactant or any combination thereof. 8.The method of claim 7, wherein the organic acid is citric acid, atricarboxylic acid, tartaric acid, succinic acid, malic acid, asparticacid, glutaric acid, adipic acid, suberic acid, oxalic acid, aceticacid, fumaric acid or any combination thereof.
 9. The method of claim 2wherein the thin film is formed of a metal, a metal nitride, a metalsilicide or a polysilicon.
 10. A cleaning method comprising: treating asubstrate with an aqueous solution comprising an oxidizer; rinsing thesubstrate with deionized water to remove the aqueous solution comprisingthe oxidizer; drying the substrate; and treating the substrate with asolution comprising a surface charge controlling agent, a fluorine baseddeoxidizer and deionized water.
 11. The method of claim 10, furthercomprising, after treating the substrate with the solution: treating thesubstrate with the aqueous solution comprising the oxidizer; rinsing thesubstrate with deionized water to remove the aqueous solution comprisingthe oxidizer; and drying the substrate.